Create MEX-Files

To create a MEX-file for a user-written fixed-point C S-function on either Windows^® or UNIX^® systems:

In your S-function, include fixedpoint.c and fixedpoint.h. For more information, see Structure of the S-Function.
Pass an extra argument, -lfixedpoint, to the mex command. For example,
```
mex('sfun_user_fxp_asr.c','-lfixedpoint')
```